Which statement is true of all matter?
a. it has mass
b. it can be seen
c. it exists only as a solid.
d. it maintains its shape and size.
my mind is blank, and i can't seem to remember.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.